YO13 - IgG4-related pseudo-tumor of the kidney and multiple organ involvement mimicked malignancy

Case summary

Background: Immunoglobulin G4 (IgG4)-related disease is a rare immune-mediated fibroinflammatory condition, characterized by infiltration of IgG4 positive plasma cells and storiform fibrosis. The clinical presentation included fibrosis of affected organs and pseudotumor formation occasionally mimic malignancy.

Aims: To present a case of IgG4-related kidney disease mimicking renal cell carcinoma

Method: Case report

Result: 53-year-old male with an unremarkable previous medical history presented with painless gross hematuria, fever and anemic symptom for 3 months. Laboratory tests showed microcytic anemia, normal creatinine levels and numerous white blood cells in urine. CT chest and abdomen revealed an infiltrative heterogenous hypoenhancing lesion at right kidney size 7.5 x7.9 x8.5cm, a hypoenhancing lesion in hepatic segment IVa/VIII size 6.8x3.8 cm, diffuse intraabdominal lymph node enlargement up to 1.8 cm and multiple lung nodules. The initial clinical and radiologic findings were highly suggestive of malignancy. The differential diagnosis is renal cell carcinoma and lymphoma. Liver biopsy was performed and shown chronic inflammation and fibrosis. Subsequently renal biopsy was done and revealed chronic interstitial nephritis, focal interstitial fibrosis and prominent plasma cell infiltration. Immunohistochemistry from renal biopsy revealed positive for CD20, CD3, CD38, CD138, IgG (210 cells/HPF) and IgG4/IgG-positive cell ratio was 54%. In situ hybridization for kappa and lambda light chain showed polyclonal plasma cell with kappa to lambda ratio of 4:1. Serum IgG4 level was more than 5,840 mg/dL. These findings made diagnosis of IgG4 related kidney disease. Prednisolone 60 mg/day was given and gradually reduced to 10 mg five months thereafter. After 3 months of therapy, a follow-up CT scan showed decrease size of right renal mass to 6.1 x7.3 x6.2 cm, nearly complete resolved of liver lesion and some prior pulmonary nodules.

Conclusion: IgG4 related kidney disease can present with pseudotumor and can be misdiagnosed as a malignant tumor. Awareness of this condition and proper investigation including histopathology and serum IgG4 level should be considered in case of highly suggestive patient.

Clinical trial identification

Editorial acknowledgement